1. Field
The present disclosure is directed to a method and apparatus for scheduling user equipment uplink transmissions on an unlicensed carrier.
2. Introduction
Presently, users use portable devices, otherwise known as User Equipment (UE), such as smartphones, cell phones, tablet computers, selective call receivers, and other wireless communication devices, on Long Term Evolution (LTE) networks. Users use the portable devices to download files, music, e-mail messages, and other data, as well as to watch streaming video, play streaming music, play online games, surf the web, and engage in other data intensive activities. Because of large amounts of downloaded data as well as large amounts of users, LTE carriers can now use unlicensed spectrum to complement the bandwidth of their LTE networks to provide faster data to users. This allows the users to download data faster on their portable devices. The unlicensed spectrum can include spectrum at 5 GHz, such as used by WiFi, and other unlicensed spectrum. LTE technology can be deployed in unlicensed spectrum using a carrier aggregation framework where a primary cell uses licensed spectrum, and a secondary cell is deployed in the unlicensed spectrum. Transmissions on the unlicensed spectrum carrier typically have to follow Discontinuous Transmission requirements (DCT requirements) due to regulatory requirements and due the need to co-exist with other wireless systems, such as Wi-Fi systems, LTE devices, such as UEs, and base stations, such as Enhanced Node-B's (eNBs), operating in the same spectrum. In some regulations, a LTE device may be required to perform Listen-Before-Talk (LBT) prior to transmitting on a carrier. If the device finds the channel is busy, then it should defer its transmission until the carrier becomes clear.